Linked Questions

69
votes
10answers
7k views

Should zero be followed by units? [duplicate]

Today at a teachers' seminar, one of the teachers asked for fun whether zero should be followed by units (e.g. 0 metres/second or 0 metre or 0 moles). This question became a hot topic, and some ...
-1
votes
1answer
109 views

How can we use zero in physics [duplicate]

Is better to say the e.g. kinetic energy is 0 joule or kinetic energy is 0 ? since 0*joule equals 0.Is a mathematical concept behind because in many books i find both ways.
0
votes
1answer
61 views

Can I say that two different quantities are zero? [duplicate]

I started to learn basics of physics in a university. I know that it is wrong to compare for example pressure and length, like $2\mbox{ Pa}\ne 2\mbox{ m}$. But from algebra I know that $0=0\cdot 2\...
0
votes
1answer
44 views

Is 0 of anything the same as 0 of any other thing? [duplicate]

So, we know that in physics, units matter. 2 cm is different from 2 newtons which is different from 2 seconds. But what if the number is 0? Is 0 of any unit the same as 0 of any other unit?
35
votes
8answers
30k views

Is there a symbol for “unitless”?

I'm making a table where columns are labelled with the property and the units it's measured in: Length (m) |||| Force (N) |||| Safety Factor (unitless) ||| etc... I'd like not to write "unitless" ...
26
votes
6answers
5k views

Why is the meter considered a basic SI unit if its definition depends on the second?

The metre is the length of the path travelled by light in vacuum during a time interval of 1  ⁄ 299792458 of a second. – 17th CGPM (1983, Resolution 1, CR, 97), source The meter (or metre) is ...
35
votes
2answers
24k views

Square bracket notation for dimensions and units: usage and conventions

One of the most useful tools in dimensional analysis is the use of square brackets around some physical quantity $q$ to denote its dimension as $$[q].$$ However, the precise meaning of this symbol ...
9
votes
4answers
1k views

Is the number 1 a unit?

In dimensionless analysis, coefficients of quantities which have the same unit for numerator and denominator are said to be dimensionless. I feel the word dimensionless is actually wrong and should be ...
14
votes
1answer
2k views

What is a base unit in the new SI, and why is the ampere one of them?

One question that comes up pretty much always in introductory electromagnetism courses is Why the base unit of electrical measurements is the ampere and not the coulomb, and the usual answer is that ...
4
votes
1answer
975 views

Buckingham-$\Pi$ theorem application: the case of only 0 or 1 dimensionless groups?

In dimensional analysis, we might consider a problem like: $$ f(q_1, q_2, ..., q_{n-1}) = q_{n} $$ where $q_i$ are physical quantities of interest. In order to determine how many $\Pi$ groups can be ...
0
votes
3answers
243 views

Units of observables in quantum mechanics

Observables in quantum mechanics are described by Hermitian operators $\hat A: V \to V$, where $V$ is the Hilbert space of states. Examples include the $x$-coordinate operator $\hat x$, the $x$-...
-3
votes
1answer
309 views

How can Maxwell's equations be correct if the terms have different units on both sides of the equation?

For instance, the divergence of the magnetic field has units but it's equated to zero?
2
votes
3answers
564 views

Are the 7 base quantities in SI system really independent?

In a typical description of the 7 base quantities of the SI system we see the following two points: All other quantities can be derived from them. They are "independent". My question is about the ...
3
votes
2answers
94 views

How are the seven base units related to each other?

How are the seven S.I. fundamental or base units of measurement of physical quantities interrelated or dependent on other base units: These seven SI base quantities are defined by universal constants....